The fabrication of printed electronic circuits using solution-based electroconductive materials at low temperature is essential for the realization of modern printed electronics including transistors, photovoltaic cells, and light-emitting devices. Despite the progress in the field of semiconductor solution materials, reliable electrodes are always fabricated by a vacuum deposition process resulting in only partially solution-processed devices. In this paper, we show that planar phthalocyanine-conjugated Au nanoparticles (NPs) significantly improve the interparticle-carrier-transport properties. The deposition of a solution of the Au NPs under ambient conditions results in an electroconductive metallic thin film without further post-treatment. Maximum conductivity reaches >6600 S cm−1 and the conductivity remains unchanged for at least 1 year under ambient conditions. The all-solution-processed organic field-effect transistor (OFET) fabricated under ambient conditions exhibits mobility values as high as 2 cm2 V−1 s−1, the value of which is comparable to OFET devices having vacuum-deposited Au electrodes.